The Gospel of the Lord Jesus Christ is the central truth of Christianity, for it is only through sincere faith in the Gospel that one can come into a saving relationship with the LORD God, through His Son, Jesus.
Gospel literally means "good news." We really need good news because there is bad news for each one of us--we are all born sinners. Romans 3:23, "For all have sinned, and come short of the glory of God."
Our sins have alienated us from God, making us His enemy, and powerless to do anything to save ourselves from His well-deserved wrath. Isaiah 59: 1-2, "Behold, the LORD's hand is not shortened, that it cannot save; neither His ear heavy, that it cannot hear: But your iniquities have separated between you and your God, and your sins have hid His face from you, that He will not hear."
Before coming to Christ, we are all dead in trespasses and sins while we walk in this world, and are condemned to eternal death and Hell when our time here ends. Ephesians 2:1, "And you who were dead in trespasses and sins. . ." Romans 6:23a, "The wages of sin is death. . . "
But it is right here where the Gospel brings us good news! Romans 6:23b continues: ". . .but the gift of God is eternal life through Jesus Christ our Lord." The LORD God, who is rich in mercy, has Himself made a way of salvation for lost sinners!
According to God's predetermined plan, the Eternal Son of God took upon Himself a human nature, and was born into the family of man, in order to do for us what we could not do for ourselves: Jesus of Nazareth lived a sinless life, and then went to a cross to bear the sins, punishment, and wrath which rightfully belonged to His people. He suffered, died and was buried. Three days later, He rose from the grave, defeating death, and proving that He is both Lord and Christ.
We are Saved by Faith Alone Which Comes by God's Grace Alone
Romans 10:9-10 says, "that if you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved; for with the heart a person believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation." (NASB)
Ephesians 2:8-9 says, "For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast." (NASB)
Salvation is thus the work of God alone from beginning to end.